“Something like a neutron star fits the bill reasonably well actually,” says Dr Ingrid Stairs, an astrophysicist from the University of British Columbia in Vancouver, Canada.

“But exactly what physics is going into producing this very energetic burst of radio waves we don’t really know yet.”

Two stars merging

Two neutron stars colliding with each other is another possibility.

According to Shriharsh Tendulkar, an astronomer at McGill University in Montreal, Canada, this is one of the main theories, but the scenario only works for cosmic signals that are only seen once, as the stars are destroyed in the process.

“It’s a cataclysmic event – it doesn’t work for fast radio burst repeaters,” he says.

Most of the fast radio bursts picked up by telescopes in the last decade or so are seen once then disappear.

Yet, two elusive signals have been found that burst into life again and again – and for these, there must be a different explanation.

Blitzar

A blitzar is a rapidly spinning neutron star which collapses under its own weight and forms a black hole.

Again, this ends in the destruction of the star, so could not produce a repeating signal.

Black hole

Black holes are implicated in many theories – from a neutron star falling into a black hole to a collapsing black hole or dark matter hitting one.

“They come from all over the sky pretty much and many different distances – they must be associated with many different galaxies,” she told Newsday on BBC World Service.

“It just seems completely inconceivable that there could be that many different alien civilisations all deciding to produce the same kind of signal in the same way – that just seems highly improbable.”

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